- A copy of Baldi's Basics (any version and possibly the challenge demo)
- A copy of UABE (Unity Asset Bundle Extractor
Be sure that you have these before starting!
First, open up UABE, and go to File, Open, and find the shared assets files in BALDI_Data.
Here's what each one represents.
0 = Warning Screen
1 = Title
2 = Everything in-game
3 = Death screen stuff
4 = You win
5 = Secret ending stuff
6 = Test room stuff
And now, choose which one, and make sure the file extension is read as .assets
and not anything else.
Next, select everything that ends in Texture2D, and then click plugins and extract to .png. You may need to create a folder for each individual sharedassets file, or put all of them into one. It's really your preference.
Once you have that, now it's time to modify the sprites! I can't tell you what type of art to design, as it's your mod, and it's completely up to you, although I'd say make the sprites a bit 3D, maybe use Paint 3D and paste the model into the art program you're using. (I personally use Krita, but again it's preference.)
Now finally, once you've saved the sprites, go back to UABE and select the sharedassets file you selected earlier, select the Texture2D files again and then click plugins, batch import, and then after that click OK. If it doesn't give you the option to save it, click OK on the main view and it should appear then. Once you do that, save it to a place that's NOT in BALDI_Data, because if you do, the file will not save properly, because UABE does not allow renaming or doing something to sprites while exporting the file. Then after you've finished and are done exporting the file, select the file you exported, and drag it into BALDI_Data. Do replace the file, because that's how it saves.
Now that you've saved your sprites, you should be able to see them in-game!
So yeah, you can modify the sprites and export the sprites whenever, as long as you save them into the game's files in BALDI_Data!